(1) Field of the Invention
The present invention relates to various mast shapes, in which the mast shapes minimize the production of visible, electro-optic, infrared and radar cross section wake signatures produced by water surface piercing masts.
(2) Background of the Invention
The contribution of submarines in littoral regions has become increasingly important as modern electronic warfare support systems proliferate. While on littoral missions, submarines invariably spend a significant time at periscope depth with one or more masts deployed through the water surface. To minimize the probability of submarine detection in the littoral regions, it is critical that mast wake signatures be minimized or eliminated. A surface piercing submarine mast typically produces signatures (i.e., spray, foam and waves) that are observable by visual, electro-optic, infrared and radar means.
One important parameter in wake signature reduction is thickness to chord ratio. Typically, the hydrodynamic loads and functional volume requirements on a submarine mast constrain the thickness to chord ratios in the range of 0.5–0.7.
Streamlining significantly reduces a visible wake by reducing bow waves and spray. Streamlining also produces lower trailing edge angles that result in reduced vortex shedding. Reduced vortex shedding minimizes generation of and mixing of bubbles and thus reduces a visible white water wake. However, the low thickness to chord ratio foils that have smaller wakes produce high lifts at angle of attack, have high wave slap loads, reduce usable internal space and take up more space in the submarine when the foils are not erected. Above 15–20° angles of attack, low thicknesses to chord foils begin to separate and thus generate more white water. Circular cross-sections minimize space requirement problems and lift and wave slap loads, but produce high drag and large wake signatures.
Alternatively, tow tank masts have ogive shapes to minimize spray and wakes and ship bows are typically sharp to minimize spray. Determining a method to incorporate the technology of tow tank masts and ship bows may be suitable to other surface piercing masts such as surface piercing masts, hydrofoil boats and oilrig platforms. Incorporating the technology will also reduce the wave heights generated by such marine vehicles and thus may allow them to travel faster through no-wake zones. As such, an improvement to masts used on submarines would be to incorporate sharp leading edges and ogive shapes as part of the shape of the masts in order to reduce the wake signatures of the masts.